Method for producing flame and soil resistant acrylic polymer fibers containing carpet fabric



METHOD FOR PRQDUCHNG FLAME AND SOlllL RESISTANT ACRYLIC POLYMER FBERS (IGN- TAHNHNG (CARPET FAERHC Julian J. Hirshfeld and Edward V. Burnthall, Decatur, Ala, assignors, by mesne assignments, to Monsanto Chemical Company, a corporation of Delaware No Drawing. Filed July 16, 1959, Ser. No. 327,433

2 Claims. (Cl. 117-137) This invention relates to carpets, rugs and the like having an improved resistance to flame and soiling, and more particularly to a process for imparting these improvements to carpet yarns and fabrics comprising acrylonitrile polymer fibers, to compositions employed therein, and to the products resulting therefrom.

Although the prior art treats extensively on the subject of flame-proofing textile materials, the newer syn-' thetics, such as textiles containing acrylic polymer fibers have received but little attention. That is, the effort devoted to improving the flame resistant quality of acrylic polymer fibers has been practically negligible when compared with, for example, cellulosics which have received the major attention heretofore.

'It has been found, for the most part, that flame-proofing procedures, which have been especially adapted for textile materials, such as cellulosics, cannot be extended in application to materials containing acrylic polymer fibers because of their inherently distinct characteristics. For example, flame-retardant agents requiring chemical affinity with the treated textile are commonly employed to enhance the flame-resistance of cellulose containing textiles. From an evaluation of many such flame-retardants none were found to have an aflinity for polyacrylonitrile fibers. In many instances, cellulosic materials can be chemically combined with compounds known to possess flame retarding properties by virtue of the available hydroxyl groups present in cellulose. However, since acrylic polymer fibers do not possess available hydroxyl groups, chemical combination is not possible with such compounds.

Although it has been found generally difficult to improve the flame resistance of textile articles containing polyacrylonitrile fibers, the difficulties are considerably magnified in the instance of carpet fabrics containing such fibers in that the nature and use of carpets imposes restrictions on procedures and compositions that can be employed. For example, any process to be acceptable for use on carpet fabrics must not impair fiber performance characteristics which are of particular importance to the commercial success of such products. That is, fiber resiliency and crushing resistance must not be affected. Furthermore, chemical treatments, which may otherwise be suitable and effective, cannot be employed if they impart toxicity to the treated article, or if they affect the color or fastness of dyes in an adverse manner. In addition, treating agents must not be removed by continued foot-traffic or readily dusted-off the treated fabric. The treatment must be durable to household vacuum cleaning and to the use of cleaning solvents on the treated fabric. A still further requirement is that soil-resistant properties of the treated fabric must not be affected deleteriously,

i.e. the treated carpet face fabric must not be made more susceptible to soiling as a result of the treatment.

It has been a common experience of the prior art that effective flame-proofing treatments for textile materials generally tend to promote a greater susceptibility to soiling. Consequently, it has been exceedingly difficult to enhance the flame resistant quality of fabrics, such as, carpet fabrics containing acrylic polymer fibers without in turn rendering these materials more prone to soiling. Similarly, it has been found that procedures which imrates Patent ire part an increased soil-resistance to textile fabrics generally tend to make the treated fabric less resistant to flame propagation. The capability for improving both the soil and flame resistance of articles, such as acrylic polymer carpet fabrics by a single treatment has been greatly de sired, however, means for accomplishing this objective have not been provided heretofore.

It is, therefore, an object of this invention to provide acrylic polymer carpet fabrics with an improved resistance to flame and soiling.

It is another object of this invention to impart both an improved resistance to flame propagation and soiling in polyacrylonitrile carpet fabrics by means of a single treatment.

It is a further object of this invention to providea treating composition which is particularly suitable for application to the face yarns and fabrics of carpets, rugs and the like which contain acrylonitrile polymer fibers in order to impart an improved flame and soiling resistance thereto.

Still further objects and advantages of this invention will become apparent from the following description and appended claims.

It has now been found that the above and other objects of the present invention can be accomplished by a process which comprises impregnating carpet fabrics containing acrylonitrile polymer fibers with a composition comprising urea, formaldehyde and ammonium bromide. Following impregnation the treated fabric is subjected to a temperature of from 260 F. to 300 F. for a time sufficient to cause reaction of the urea and formaldehyde in situ, and to cure the resulting thermosetting resin to the water-insoluble state.

The present invention is applicable to all acrylic fibers which are formed from polymers containing at least percent by weight of acrylonitrile in polymeric form. These include fibers formed from polyacrylonitrile, copolymers, and terpolymers containing at least 80 percent of acrylonitrile plus one or more mono-olefinic monomers copolymerizable therewith, and blended polymers and copolymers in which the blend composition contains at least 80 percent acrylonitrile. The blended polymers, for example, may comprise a major amount of a polymer of somewhat more than 80 percent acrylonitrile and a minor amount of another polymer or copolymer, the polymers being so proportioned that the blended polymer contains at least 80 percent acrylonitrile by weight.

The copolymers and terpolymers of at least 80 percent acrylonitrile may contain copolymerized therewith such other mono-olefinic monomers as acrylic, haloacrylic, and methacrylic acids; esters such as methyl, butyl, octyl, methoxymethyl, and chloroethyl methacrylates and the corresponding esters of acrylic and haloacrylic acids; methacrylonitrile; vinyl and vinylidine halides such as methacrylonitrile; vinyl and vinylidine halides such as vinyl chloride, Vinyl fluoride, vinylidine chloride, l-fluoro-lchloroethylene; vinyl carboxylates such as vinyl acetate, vinyl chloroacetate, vinyl propionate, and vinyl stearate; N-vinylimides such as N-vinylphthalimide, and N-vinylsuccinimide, N-vinyllactams such as N-vinylcaprolactam and N-vinylbutyrolactam; aryl compounds such as styrene and vinyl naphthalene, and other compounds such as methyl vinyl ketone, methyl furnarate, methyl vinylsulfone, fumaronitrile, maleic anhydride, the vinyl pyridines such as Z-Vinylpyridine, and 4-vinylpyridine, the vinyl-substituted alkyl pyridines such as 4-ethyl-2-vinylpyridine, 5- ethyl-Z-vinylpyridine, and Z-methyl-S-vinylpyridine; the isomeric vinylpyrazines, the various isomeric vinylquinolines, the vinylimidazoles and the vinylbenzoxazoles.

The blended polymers containing at least 80 percent acrylonitrile may, for example, comprise a major amount of a polymer (A) containing at least percent acrylonitrile and up to 15 percent of one of the above-named mono-olefinic monomers copolymerizable therewith and a minor amount of a polymer (B) containing one of the vinyl-substituted alkyl pyridine monomers noted above and another of the above-named mono-olefinic monomers or acrylonitrile copolymerized therewith. These blended polymer compositions preferably contain from 50 to 98 percent of polymer (A), containing at least 85 percent acrylonitrile and up to 15 percent of another mono-olefinic monomer copolymerizable therewith, and from 2 to 50 percent of polymer (B), containing at least 30 percent of a vinyl-substituted alkyl pyridine monomer and up to 70 percent of another mono-olefinic monomer copolymerizable therewith, polymers (A) and (B) being so proportioned that the polymer blend contains from 2 to 15 percent of the vinyl-substituted alkyl pyridine monomer in polymerized form.

While the present invention is particularly effective when applied to carpet yarns and fabrics composed entirely of the afre-described polymeric materials, it is also fully applicable in the case of blends containing other textile materials, such as wool, rayon, nylon, etc. That is, it is contemplated that the present process can be applied to textile materials where the major portion, i.e. in excess of 50 percent thereof, is composed of acrylic fibers which are formed from polymers containing at lease 80 percent by weight of acrylonitrile in polymeric form.

In the practice of the present invention, the carpet fabric to be treated is first impregnated with a composition comprising urea, formeldehyde and ammonium bromide as essential components. The treating composition may be readily applied from an aqueous solvent so as to impart to the fabric from about 3 to about 30 percent solids and preferably from about 4 to about percent solids based on the dry weight of said fabric. The solids can be incorporated into the aqueous so vent in the range of from about 1 percent to 35 percent or more up to the limit of solubility. The solvent is used only to facilitate deposit of the solids on the fabric to be treated since it is eliminated from the fabric by evaporation following impregnation thereof.

Any suitable apparatus can be employed in applying the treating composition to the textile fabric. In the case of carpets, it is particularly convenient to employ a movable spraying device. Such apparatus is suitably connected to a supply source of the treating solution, which can be pumped through the spray unit and on to the carpet fabric being treated. impregnation may also be accomplished by other conventional means, such as by padding or brushing.

The proportions between the essential components of the treating composition fall within definite limits. Based on percent of total weight excluding the aqueous vehicle, the ammonium bromide can be employed in an amount of from about to 70 percent with from about 30 to 50 percent being preferred; the urea may be present in an amount of from about 5 to 30 percent with from about 7 to 20 percent being preferred; and the formaldehyde may be employed in an amount of from about 5 to 60 percent with from about :10 to 4-0 percent being preferred.

As is known in the art, other aldehydes, such as acetaldehyde, glyoxal, and the like, may be substituted for the formaldehyde. However, formaldehyde is preferred, and may be obtained from a formalinsolution or may be derived from a source of formaldehyde such as paraformaldehyde, trioxymethylene and the like.

The urea and formaldehyde need not be entirely unreacted prior to use and may be employed in a form such as an essentially monomeric condensation product. However, it is necessary to prevent a resin-forming reaction during storage of these components so as to avoid the formation of water-insoluble products. For this reason, it is important that the ammonium bromide not be present with the resin-forming reactants prior to use,

in that it is a particularly effective accelerator for ureaformaldehyde condensation reactions.

In some instances, it may be desirable to include a rust inhibitor or anti-corrosion agent as a part of the treating composition. The inclusion of a rust inhibitor may be desirable where treated fabrics are likely to contact metals, such as metal furniture and the like, since the ammonium bromide component of the treating composition may cause some slight corrosion on metals in contact therewith. Any compound employed for this purpose must be compatible with the essential components of the treating composition and should not adversely affect the performance thereof. It has been found that the compound guanyl urea phosphate is uniquely suited for this purpose in that it possesses flame-retardant as well as rust-inhibiting properties, and is otherwise satisfactory. The guanyl urea phosphate can be employed in an amount of from about 1 to about 7 percent, based on the total weight of the treating composition.

A plasticizer or softening agent may also be included as an optional ingredient in the treating composition of this invention in order to provide a more desirable hand or texture to the treated fabric. It has been found that the cationic softening agent hydroxylalkyl glyoxalidine can be employed with particular advantage for this purpose. The softening agent is normally employed in amounts of from about 1 to about 15 percent, based on the weight of the total composition. i

Following impregnation with the afore-described treating composition, the treated fabric is heated to cause reaction of the urea and formaldehyde in situ, and to cure the resinous finish resulting therefrom. Heating can be carried out in one or two steps to obtain the same ultimate result. That is, drying and curing of a treated fabric may be accomplished in separate steps or in a single operation, if this is preferred. When drying is carried out as a separate step, it may be done either at normal ambient air temperatures or at elevated temperatures up to 212 F. or higher. Following the drying operation, whether it be accomplished at normal temperatures or by heating, the dried impregnated textile is brought to a temperature within the range of about 260 F. to 300 F. The higher the temperature, the shorter is the period of heat treatment. Thus, drying the impregnated textile for 20 minutes in an oven maintained at a temperature of about 210 F. followed by heating at a higher temperature, for example, for 8 minutes at 270 F. or for 4 minutes at 300 F., is generally effective in obtaining the desired results. These specific time and temperature periods are merely illustrative of those that can be employed. Because of the presence of the ammonium bromide which catalyzes the ureaformaldehyde condensation reaction, the time necessary to form and cure the resinous finish is considerably shortened from what would otherwise be necessary.

In addition to accelerating the above-described condensation reaction, the ammonium bromide component of the treating composition functions in cooperation with the other essential ingredients of the composition to provide the superior results realized in the practice of this invention. This is made possible by virtue of the fact that the ammonium bromide becomes physically bound in the resinous finish, and is not readily removed.

from the treated fabric.

Although it is not our intention to be limited by any theory relating to the means by which the results of this invention are achieved, it is believed that the superior flame-retardant results are realized, at least in part, from the coincidental fact that ammonium bromide sublimes at practically the ignition temperature of acrylic fibers, i.e. 542 F. and 540 F. respectively. Since the ammonium bromide undergoes an endothermic phase transition at the ignition temperature of the acrylic fiber, it is believed that sufiicient heat is absorbed during the phase change to reduce the temperature of the ignited fabric below that which is necessary for continuance of a flame.

As has been noted hereinabove, the treatment of fabrics in accordance with this invention not only provides improved resistance to flame, but concomitant therewith is a resulting improvement in resistance to soiling. The improvement in soiling resistance is accomplished in part by the smooth surface imparted to the treated fibers. That is, the indentations and channels normally present in the untreated fiber, which provide collection sites for the deposition of dirt particles, are reduced by the finish provided in the practice of this invention.

Since the treating composition possesses anti-static properties, this is a further factor contributing to the improvement of soil resistance in treated fabrics. As is well known, one of the mechanisms of soil deposition is via the build-up of an electrostatic charge on fabric fibers, which then attracts an uncharged or oppositely charged particle. In addition to the collection of dirt particles of micron size, lint or dust of a larger dimension may also be attracte/d. The hydrophobic fibers, such as those composed of acrylic polymers, because of their inherent characteristics, one of which is their hydophobicity, can build up and hold a larger electrostatic charge than the hydrophilic fibers, and consequently soiling from static build-up is a generally more serious problem.

Another property not pertinent to soiling but, nevertheless, an important consideration is that of the static electrical discharge experienced by a person when he scuffs his feet across a carpet or rug and touches a metal object, such as a door handle. The higher the charge capable of being built-up, the greater the shock to the person. Since the hydrophobic fibers are capable of building up and holding such charges, they present a particular problem in this respect. For these and other reasons, it becomes desirable to suppress the static property in these materials.

The effectiveness of the composition of this invention in dissipating static electrical charges on synthetic acrylic polymer fibers was determined by a comparative test of an untreated and treated acrylic polymer fabric. In making the determinations static electricity was induced on the test samples by means of Hayeks apparatus. The amount of static retained on the test samples over a given period of time was measured by means of a microamperemeter. Hayeks apparatus consists of a metallic wheel rotating around its axis which is driven by a motor. The sample to be examined is fixed at the periphery of the wheel in close contact with a swatch of wool which is mounted on a copper plate and does not move. The friction between the rotating sample and the wool swatch generates static electricity the amount of which is shown on the connected microamperemeter. After two minutes of friction generation the amount of static shown on the dial is recorded, the contact between the sample and the wool swatch is broken and the wheel continues to rotate in order to dissipate the accumulated static. The time (expressed in minutes and seconds) necessary for the examined sample to dissipate half of the static (expressed in microamperes) accumulated during the two minutes contact with the wool is the criterion for the effectiveness of the treatment. This value may be termed the half life of the static charge. If the half life exceeds ten minutes there is considered to be little anti-static property present.

Example I A swatch of fabric loomed from acrylic fibers composed of a blend of a copolymer of.94 percent acrylonitrile and 6 monium bromide, 16 parts of urea, 16 parts of formaldehyde, 3 parts of guanyl urea phosphate, and 10 parts of hydroxylalkyl glyoxalidine. The amount of solids deposited on the impregnated fabric constituted 5.2 percent by weight based on the dry fabric.

Following impregnation, the treated fabric was dried for 20 minutes ata temperature of 210 F. It was, thereafter, heated to a curing temperature of 280 F. for 8 minutes to complete the treatment. After conditioning the treated fabric for a day at a temperature of F. and a relative humidity of 33 percent, a static accumulation test was conducted on the fabric in accordance with the above-described method.

A second swatch of untreated fabric loomed from the same acrylic polymer fibers as that noted above was also tested for static accumulation in accordance with the same test method. The comparative test results follow:

In order to determine the extent of improvement in the flame resistant property of carpet fabrics treated in accordance with the present invention, the so-called match test was employed. In this test, a swatch of carpet fabric measuring 8 inches by 10 inches is placed in a draft-free enclosure. Ten safety paper-type matches are ignited one at a time and placed randomly on the surface of the carpet. The resistance of the test sample to flame is expressed as .that percentage of the ten matches from which flame propagation did not occur.

The following experiments demonstrate the improvement realized in flame resistance with carpet fabrics treated accordingly to the present invention.

Example 11 A swatch of carpet fabric measuring 8 by 10 inches and containing acrylic fibers composed of a blend of a copolymer of 94 percent acrylonitrile and 6 percent vinyl acetate with a copolymer of 50 percent acrylonitrile and 50 percent methylvinylpyridine so proportioned that the final product contains 6 percent methylvinylpyridine in polymerized form was impregnated with an aqueous solution having a solute which contained the following ingredients in parts by weight: 30 parts of ammonium bromide, 19 parts of urea, 38 parts of formaldehyde, 4 parts of guanyl urea phosphate and 9 parts of hydroxylalkyl glyoxalidine. The solids content deposited was 6.0 percent calculated on the weight of the dry fabric.

After conditioning for a day at room temperature, the treated carpet fabric was tested for flame-resistance in accordance with the above-described procedure. The test rating obtained was 100 percent, i.e. all of the ignited matches failed to propagate flame; whereas, an untreated control was given a rating of 10 percent with flame propagation having occurred from 9 of the 10 ignited matches.

Example III .A swatch of carpet fabric containing a blend of per- I cent acrylic polymer fibers with 20 percent wool was impregnated with an aqueous treating agent consisting of the following ingredients in parts by weight: 68 parts of ammonium bromide, 19 parts of urea, 11 parts of formaldehyde and 2 parts of guanyl urea phosphate. The amount of solids deposited was 3.6 percent based on the weight of the dry fabric.

Following impregnation, the treated fabric was dried for 15 minutes at a temperature of 210 F. It was, thereafter, heated to a temperature of 280 F. for 8 '2' minutes to complete the treatment. After conditioning the treated fabric was tested for flame resistance. The rating obtained was 100 percent as opposed to 70 percent for an untreated control.

Example IV A swatch of carpet fabric containing a blend of 80 percent acrylic polymer fibers with 20 percent rayon was impregnated with an aqueous treating agent consisting of the following ingredients in parts by weight: 58 parts of ammonium bromide, 16 parts of urea, 18 parts of formaldehyde, and 8 parts of guanyl urea phosphate. The solids deposited on the fabric represented 10.4 percent by weight of the dry fabric.

Following impregnation, the treated fabric was dried for 15 minutes at a temperature of 210 F. after which the temperature was raised to 280 F. for 8 minutes. Following conditioning, the treated fabric was tested for flame-resistance and the rating obtained was 100 percent as opposed to Zero percent for the untreated control.

Example V A swatch of carpet fabric containing a blend of 70 percent acrylic polymer fibers with 30 percent nylon was impregnated with an aqueous treating agent consisting of the following ingredients in parts by weight: 40 parts of ammonium bromide, 32 parts of urea, 27 parts of formaldehyde and 1 part of guanyl urea phosphate. The solids deposited on the fabric constituted 4.1 percent by weight based on the weight of the dry fabric.

Following impregnation, the treated fabric was dried for 15 minutes at a temperature of 210 F. for 8 minutes. The treated fabric was conditioned at room temperature for 24 hours. The test rating obtained for the fabric so treated was 100 percent as opposed to 70 percent for the untreated control.

The carpet fabrics of Examples II, III, IV and V above were subjected to a further soiling test to illustrate the improved resistance to soiling realized by treatment in accordance with this invention. Resistance to soiling was determined by a controlled floor-soiling service test. That is, both a treated test specimen and an untreated control were exposed to 15,000 passes of foot traffic, which is equivalent to about 8 months of normal household use, and thereafer compared for the degree of soiling resulting from such exposure. The extent of soiling was determined by means of an optical technique employing a Photovolt refiectometer equipped with a green filter and adapted for taking light reflectance measurements of the carpet surfaces. Reflectance values were taken prior to exposure to soiling and immediately thereafter. The test results are expressed as a percentage loss in light reflectance resulting from exposure to the test conditions.

While the above examples and description of this invention have dealt primarily with carpet fabrics containing acrylic polymer fabrics, since the invention has been particularly adapted for application thereto, it is to be understood that the present invention can also be applied to other textile articles containing acrylic polymer fibers such as draperies, furniture coverings, upholstery and the like.

As many variations within the spirit and scope of this invention will occur to those skilled in the art, it is to be understood that the present invention is not limited to specific embodiments thereof except as set forth in the appended claims.

What we claim is:

1. A method for imparting flame and soiling resistance to carpet fabric and the like containing a major portion of acrylic fibers which are formed from polymers containing at least percent by weight of acrylonitrile in polymeric form comprising impregnating said fabric with an aqueous solution containing from about 1 percent to about 35 percent by weight of a solute comprising the following ingredients in the specified proportions by weight: (1) from about 30 to 50 parts of ammonium bromide, (2) from about 7 to about 20 parts of urea, (3) from about 10 to about 40 parts of formaldehyde, (4) from about 1 to about 7 parts of guanyl urea phosphate, and (5) from about 1 to about 15 parts of hydroxylalkyl glyoxalidine where (l), (2), (3), (4) and (5) are supplied in an amount of from about 4 percent to about 15 percent based on the weight of said fabric; and thereafter drying the impregnated fabric followed by heating the dried fabric to a temperature within the range of about 260 F. to about 300 F. until a water-insoluble finish is formed thereon.

2. A method for imparting flame and soiling resistance to carpet fabric and the like containing a major portion of acrylic fibers formed from a blend of a copolymer of 94 percent acrylonitrile and 6 percent vinyl acetate with a copolymer of 50 percent acrylonitrile and 50 percent methylvinylpyridine said copolymers being so proportioned that the final product contains 6 percent methylvinylpyridine in polymerized form, said method comprising impregnating said fabric with an aqueous solution containing from about 1 percent to about 35 percent by weight of a solute comprising the following ingredients in the specified proportions by weight: (1) 55 parts of ammonium bromide, (2) 16 parts of urea, (3) 16 parts of formaldehyde, (4) 3 parts of guanyl urea phosphate, and (5) 10 parts of hydroxylalkyl glyoxalidine wherein (1), (2), (3), (4) and (5) are supplied in an amount of 5.2 percent based on the weight of said fabric; and thereafter drying the impregnated fabric by heating to a temperature of 210 F. followed by heating to a temperature of 280 F. until a water-insoluble finish is formed on said fabric.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A METHOD FOR IMPARTING FLAME AND SOILING RESISTANCE TO CARPET FABRIC AND THE LIKE CONTAINING A MAJOR PORTION OF ACRYLIC FIBERS WHICH ARE FORMED FROM POLYMERS CONTAINING AT LEAST 80 PERCENT BY WEIGHT OF ACRYLONITRILE IN POLYMERIC FORM COMPRISING IMPREGNATING SAID FABRIC WITH ABOUT 35 PERCENT BY WEIGHT OF A SOLUTE COMPRISING THE FOLLOWING INGREDIENTS IN THE SPECIFIED PROPORTIONS BY WEIGHT: (1) FROM ABOUT 30 TO 50 PARTS OF AMMONIUM BROMIDE, (2) FROM ABOUT 7 TO ABOUT 20 PARTS OF UREA, (3) FROM ABOUT 10 TO ABOUT 40 PARTS OF FORMALDEHYDE, (4) FROM ABOUT 1 TO ABOUT 7 PARTS OF GUANYL UREA PHOSPHATE, AND (5) FROM ABOUT 1 TO ABOUT 15 PARTS OF HYDROXYLALKYL GLYOXADIENE WHERE (1), (2), (3), (4) AND (5) ARE SUPPLIED IN AN AMOUNT OF FROM ABOUT 4 PERCENT TO ABOUT 15 PERCENT BASED ON THE WEIGHT OF SAID FABRIC; AND THEREAFTER DRYING THE IMPREGNATED FABRIC FOLLOWED BY HEATING THE DRIED FABRIC TO A TEMPERATURE WITHIN THE RANGE OF ABOUT 260* F. TO ABOUT 300* F. UNTIL A WATER-INSOLUBLE FINISH IS FORMED THEREON. 